Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$170.83	4.555%	$178.6113	$178.61	$178.60	$178.60
Purchase #2	$181.86	8.149%	$196.6798	$196.68	$196.70	$196.70
Purchase #3	$193.96	8.712%	$210.8578	$210.86	$210.85	$210.90
Purchase #4	$67.38	3.621%	$69.8198	$69.82	$69.80	$69.80
Purchase #5	$186.51	8.118%	$201.6509	$201.65	$201.65	$201.70
Purchase #6	$79.77	11.778%	$89.1653	$89.17	$89.15	$89.20
Purchase #7	$115.58	7.168%	$123.8648	$123.86	$123.85	$123.90
7 purchase totals =	$995.89		$1,070.6497	$1,070.65	$1,070.60	$1,070.80